Re: Cleaning SCT corrector plate

"adm" <adm1@xxxxxxxxxxx> wrote in message
> Dear All,
> I have a Meade LX200GPS 10" and the corrector plate appears to be quite
> dirty after the last few months of observing. Looking at it from an
> angle, there aren't any smudges, but there is quite a lot of stuck on
> dust and general crud and the surface appears rather matte. I'd like to
> clean it, but am really quite scared of touching the plate at all.
> Anyway, after doing some reading up on the web, some people recommend
> removing the corrector plate to clean it on the bench - which seems
> quite sensible to me as I can then use lots of solvent to wash it with
> and hopefully avoid some of the issues of streaking I would probably get
> if I attack it with wipes and solvent in situ.
> However - how easy of a procedure is it to remove, and what are the
> chances of putting it back out of alignment ? I am quite "handy" with
> most things - microelectronics, mechanics etc, but have zero experience
> fiddling with optics other than using this scope and colimating it. I
> did install the Peterson EZ-Focus and EZ-Clutch kits with no problems,
> so I'm not really worried about getting the thing apart and back
> together again, just worried about possible effects of misalignment
> etc....
> Any advice from anyone who has been there and done that ?
You may well find that a really gentle 'brush', will remove a large
quantity of the 'muck', without involving a full clean, A really soft
'lens' brush, or a brand new ladies 'foundation' brush, may remove most of
the problem.I'd suspect a large percentage is pollen, which can often be
removed this way. However it unfortunately can stick (especially if left
in place for a while), and if there is enough of it, a full clean may be
For a 'full' clean, removal is the best option. The key is to ensure that
you know which way round it goes (front/back, and rotationally), and where
all the spacers are positioned around the edge. Normally the corrector is
marked, but if not, use a little drop of paint, and mark the edge, before
taking it out. The scope will still require re-collimation after
re-assembly, but this ensures that if it was rotationally aligned at the
factory for reasonable performance, you do go back into the same spot.
Remember also that for a full 'wash', you will want to remove the
secondary assembly as well, and this too should be marked to maintain
rotational alignment.

Best Wishes